1. The Field of the Invention.
The present invention relates to articles of manufacture, particularly containers and packaging materials manufactured from hydraulically settable sheets. More particularly, the present invention relates to mass produced containers or parts of containers, including those used to hold, dispense, portion, or protect food, beverages, or any type of object or liquid. The hydraulically settable sheets can be used to make containers in much the same manner as paper, cardboard, plastic, polystyrene, or metals.
2. Related Applications.
This application is a continuation-in-part of U.S. patent application Ser. No. 08/019,151, entitled "Cementitious Materials for Use in Packaging Containers and Their Methods of Manufacture," and filed Feb. 17, 1993, in the names of Per Just Andersen, Ph.D., and Simon K. Hodson, now issued as U.S. Pat. No. 5,453,310. This application is also a continuation-in-part of U.S. patent application Ser. No. 08/095,662, entitled "Hydraulically Settable Containers And Other Articles for Storing, Dispensing, and Packaging Food and Beverages and Method For Their Manufacture," and filed Jul. 21, 1993, in the names of Per Just Andersen, Ph.D., and Simon K. Hodson, now U.S. Pat. No. 5,385,764. This application is also a continuation-in-part of U.S. patent application Ser. No. 08/101,500, entitled "Methods and Apparatus for Manufacturing Moldable Hydraulically Settable Sheets Used in Making Containers, Printed Materials, and Other Objects," and filed Aug. 3, 1993 in the names of Per Just Andersen, Ph.D. and Simon K. Hodson now abandoned. Each of these applications is also a continuation-in-part of U.S. patent application Ser. No. 07/929,898, entitled "Cementitious Food and Beverage Storage, Dispensing, and Packaging Containers and the Methods of Manufacturing Same," filed Aug. 11, 1992, in the names of Per Just Andersen, Ph.D., and Simon K. Hodson (now abandoned). For purposes of disclosure, each of these applications is incorporated herein by specific reference.
3. The Relevant Technology.
A. Packaging Containers.
Advanced processing and packaging techniques presently allow an enormous variety of liquid and solid goods to be stored, packaged, or shipped while being protected from harmful elements. Packaging protects goods from environmental influences and distribution damage, particularly chemical and physical influence and damage. Packaging also provides a medium for the dissemination of information to the consumer, such as the origin of manufacture, contents, advertising, instructions, brand identification, and pricing. Packaging helps protect an enormous variety of goods from gases, moisture, light, microorganisms, vermin, physical shock, crushing forces, vibration, leaking, or spilling. In addition, food or beverage products may be dispensed using specific packaging aids, such as disposable cups, plates, or boxes (such as the "clam shell" frequently used in the fast food industry for burgers, sandwiches, and salads).
Typically, most containers and cups (including disposable containers) are made from paper, cardboard, plastic, polystyrene, glass, and metal materials. Each year over one hundred billion aluminum cans, billions of glass bottles, and thousands of tons of paper and plastic are used in storing and dispensing soft drinks, juices, and beer. Outside of the beverage industry, packaging containers, and especially disposable containers, made from such materials are ubiquitous.
In order to keep certain items hot, containers made from polystyrene have been used. Although paper or plastic coated containment products can be equipped with special handles, polystyrene containers have remained the superior disposable container of choice when insulation is required, because of insulation capabilities, cost, and stability.
In spite of the more recent attention that has been given to reduce the use of paper, cardboard, plastic, polystyrene, and metal materials, they continue to be used because of strength properties and mass producibility. Moreover, for any given use for which they are designed, such materials are relatively inexpensive, lightweight, easy to mold, strong, durable, and resistant to degradation during use.
B. The Impact of Paper, Plastic, Glass and Metal.
Recently there has been a debate as to which of these materials (e.g., paper, cardboard, plastic, polystyrene, glass, or metal cans) is most damaging to the environment. Consciousness-raising organizations have convinced many people to substitute one material for another in order to be more environmentally "correct." The debate often misses the point that each of these materials has its own unique environmental weaknesses. One material may appear superior to another when viewed in light of a particular environmental problem, while ignoring different, often larger, problems associated with the supposedly preferred material. In fact, paper, cardboard, plastic, polystyrene, glass, and metal materials each has its own unique environmental weaknesses.
For example, while polystyrene itself is a relatively inert substance, its manufacture involves the use of a variety of hazardous chemicals and starting materials. Unpolymerized styrene is very reactive and therefore presents a health problem to those who must handle it. Because styrene is manufactured from benzene (a known mutagen and probably a carcinogen), residual quantities of benzene can be found in styrene. Polystyrene is very slow to degrade and discarded containers can persist for a long time.
More potentially damaging has been the use of chlorofluorocarbons (or "CFCs") in the manufacture of "blown" or "expanded" polystyrene products. This is because CFCs have been linked to the destruction of the ozone layer. In the manufacture of foams, including blown polystyrene, CFCs (which are highly volatile liquids) have been used to "expand" or "blow" the polystyrene into a foamed material, which is then molded into the form of cups, plates, trays, boxes, "clam-shell" containers, spacers, or packaging materials. Even the substitution of less "environmentally damaging" blowing agents (e.g., HCFC, CO.sub.2, and pentanes) are still significantly harmful and their elimination would be beneficial.
In light of these problems, some environmental groups have favored a temporary return to the use of natural products such as paper or wood, which are believed to be more biodegradable. Nevertheless, other environmental groups have taken the opposite view in order to minimize cutting trees and depleting the forests.
Although paper products are ostensibly biodegradable and have not been linked to the destruction of the ozone layer, recent studies have shown that the manufacture of paper probably more strongly impacts the environment than does the manufacture of polystyrene. In fact, the wood pulp and paper industry has been identified as one of the five top polluters in the United States. For instance, products made from paper require ten times as much steam, fourteen to twenty times the electricity, and twice as much cooling water compared to an equivalent polystyrene product. Various studies have shown that the effluent from paper manufacturing contains ten to one hundred times the amount of contaminants produced in the manufacture of polystyrene foam.
In addition, a by-product of paper manufacturing is that the environment is impacted by dioxin, a harmful toxin. Dioxin, or more accurately, 2,3,7,8-tetrachlorodibenzo[b,e]-[1,4]dioxin, is a highly toxic, contaminant, and is extremely dangerous even in very low quantities. The highest level of dioxin allowed in the discharge waters from paper mills is about 0.5 part per trillion. However, fish found downstream from paper pulp mills can contain nearly 200 parts per trillion of dioxin, with levels of 50 parts per trillion being not uncommon.
The manufacturing processes of metal cans (particularly those made of aluminum and tin), glass bottles, and ceramic containers utilize high amounts of energy because of the necessity to melt and then separately work and shape the raw metal into an intermediate or final product. These high energy and processing requirements not only utilize valuable energy resources, but they also result in significant air, water, and heat pollution to the environment. Further, while glass can be recycled, that portion which ends up in landfills is essentially nonbiodegradable. Broken glass shreds are very dangerous and can persist for years.
Even paper or cardboard, believed by many to be biodegradable, can persist for years, even decades, within landfills where they are shielded from air, light, and water, all of which are required for normal biodegradation activities. There are reports of telephone books and newspapers having been lifted from garbage dumps that had been buried for decades. This longevity of paper is further complicated since it is common to treat, coat, or impregnate paper with various protective materials which further slow or prevent degradation.
Another problem with paper, cardboard, polystyrene, and plastic is that each of these requires relatively expensive organic starting materials, some of which are nonrenewable, such as the use of petroleum in the manufacture of polystyrene and plastic. Although trees used in making paper and cardboard are renewable in the strict sense of the word, their large land requirements and rapid depletion in certain areas of the world undermines this notion. Hence, the use of huge amounts of essentially nonrenewable starting materials in making disposable containers cannot be sustained and is not wise from a long term perspective. Furthermore, the processes used to make the packaging stock raw materials (such as paper pulp, styrene, or metal sheets) are very energy intensive, cause major amounts of water and air pollution, and require significant capital requirements.
In light of the foregoing, the debate should not be directed to which of these materials is more or less harmful to the environment, but rather toward asking: Can we discover or develop an alternative material which will solve most, if not all, of the various environmental problems associated with each of these presently used materials?
C. Traditional Hydraulically Settable Materials.
In contrast, man has for millennia made great use of nondepletable inorganic materials such as clay or stone. Similarly, hydraulically settable materials such as those that contain hydraulic cement or gypsum (hereinafter "hydraulically settable," "hydraulic," or "cementitious" compositions, materials, or mixtures) have been used for thousands of years to create useful, generally large, bulky structures that are durable, strong, and relatively inexpensive. For example, cement is a hydraulically settable binder derived from clay and limestone, and it is essentially nondepletable.
Those materials containing a hydraulic cement are generally formed by mixing hydraulic cement with water and usually some type of aggregate to form a cementitious mixture, which hardens into concrete. Ideally, a freshly mixed cementitious mixture is fairly nonviscous, semi-fluid, and capable of being mixed and formed by hand. Because of its fluid nature, concrete is generally shaped by being poured into a mold, worked to eliminate large air pockets, and allowed to harden. If the surface of the concrete structure is to be exposed, such as on a concrete sidewalk, additional efforts are made to finish the surface to make it more functional and to give it the desired surface characteristics.
Due to the high level of fluidity required for typical cementitious mixtures to have adequate workability, the uses of concrete and other hydraulically settable mixtures have been limited mainly to simple shapes which are generally large, heavy, and bulky, and which require mechanical forces to retain their shape for an extended period of time until sufficient hardening of the material has occurred. Another aspect of the limitations of traditional cementitious mixtures or slurries is that they have little or no form stability and are molded into the final form by pouring the mixture into a space having externally supported boundaries or walls.
It is precisely because of this lack of moldability (which may be the result of poor workability and/or poor form stability), coupled with the low tensile strength per unit weight, that hydraulically settable materials have traditionally been useful only for applications where size and weight are not limiting factors and where the forces or loads exerted on the concrete are generally limited to compressive forces or loads, as in, e.g., roads, foundations, sidewalks, and walls.
Moreover, hydraulically settable materials have historically been brittle, rigid, unable to be folded or bent, and having low elasticity, deflection and flexural strength. The brittle nature and lack of tensile strength (about 1-4 MPa) in concrete is ubiquitously illustrated by the fact that concrete readily cracks or fractures upon the slightest amount of shrinkage or bending, unlike other materials such as metal, paper, plastic, or ceramic. Consequently, typical cementitious materials have not been suitable for making small, lightweight objects, such as containers or thin sheets, which are better if made from materials with much higher flexibility and tensile strength per unit weight compared to typical hydraulically settable materials.
More recently, higher strength cementitious materials have been developed which might be capable of being formed into smaller, denser objects. One such material is known as "Macro-defect Free" or "MDF" concrete, such as is disclosed in U.S. Pat. No. 4,410,366 to Birchall et al. See also, S. J. Weiss, E. M. Gartner & S. W. Tresouthick, "High Tensile Cement Pastes as a Low Energy Substitute for Metals, Plastics, Ceramics, and Wood," U.S. Department of Energy CTL Project CR7851-4330 (Final Report, November 1984).
However, such high strength cementitious materials have been prohibitively expensive and would be unsuitable for making inexpensive containers where much cheaper materials better suited for such uses (e.g., paper and plastic) are readily available. Another drawback is that MDF concrete cannot be used to mass produce small lightweight objects due to the high amount of time and effort involved in forming and hardening the material and the fact that it is highly water soluble. Therefore, MDF concrete has been limited to expensive objects of simple shape.
Another problem with traditional, and even more recently developed high strength concretes, has been the lengthy curing times almost universally required for most concretes. Typical concrete products formed from a flowable mixture require a hardening period of 10-24 hours before the concrete is mechanically self-supporting, and upwards of a month before the concrete reaches a substantial amount of its maximum strength. Extreme care has had to be used to avoid moving the hydraulically settable articles until they have obtained sufficient strength to be demolded. Movement or demolding prior to this time has usually resulted in cracks and flaws in the matrix. Once self-supporting, the object could be demolded, although it has not typically attained the majority of its ultimate strength until days or even weeks later.
Since the molds used in forming hydraulically settable objects are generally reused in the production of concrete products and a substantial period of time is required for even minimal curing of the concrete, it has been difficult to economically and commercially mass produce hydraulically settable objects. Although zero slump concrete has been used to produce large, bulky objects (such as molded slabs, large pipes, or bricks which are immediately self-supporting) on an economically commercial scale, such production is only useful in producing objects at a rate of a few thousand per day. Such compositions and methods cannot be used to mass produce small, thin-walled objects at a rate of thousands per hour.
Demolding a hydraulically settable object can create further problems. As concrete cures, it tends to bond to the forms unless expensive releasing agents are used. It is often necessary to wedge the forms loose to remove them. Such wedging, if not done properly and carefully each time, often results in cracking or breakage around the edges of the structure. This problem further limits the ability to make thin-walled hydraulically settable articles or shapes other than flat slabs, particularly in any type of a commercial mass production.
If the bond between the outer wall of the molded hydraulically settable article and the mold is greater than the internal cohesive or tensile strengths of the molded article, removal of the mold will likely break the relatively weak walls or other structural features of the molded article. Hence, traditional hydraulically settable objects must be large in volume, as well as extraordinarily simple in shape, in order to avoid breakage during demolding (unless expensive releasing agents and other precautions are used).
Typical processing techniques of concrete also require that it be properly consolidated after it is placed in order to ensure that no voids exist between the forms or in the matrix. This is usually accomplished through various methods of vibration or poking. The problem with consolidating, however, is that the more extensive the consolidation of the concrete after it has been placed, the greater the segregation or bleeding of the concrete.
"Bleeding" is the migration of water to the top surface of freshly placed concrete caused by the settling of the aggregate. Excessive bleeding increases the water-to-cement ratio near the top surface of the concrete slab, which correspondingly weakens and reduces the durability of the surface of the slab. The overworking of concrete during the finishing process not only brings an excess of water to the surface, but also some fine material, thereby resulting in inhomogeneity or nonuniformity which manifest themselves as subsequent surface defects.
For each of the foregoing reasons, as well as numerous others which cannot be listed here, hydraulically settable materials have not generally had application outside of the formation of large, slab-like objects, such as in buildings, foundations, walk-ways, or highways, or as mortar to adhere bricks or cured concrete blocks. It is completely counterintuitive, as well as contrary to human experience, to even imagine (let alone actually experience) the manufacture of small lightweight objects (such as containers comparable to the lightweight materials made from paper, plastic, or metal) from hydraulically settable materials within the scope of the present invention.
Yet, due to the more recent of the tremendous environmental impact (not to mention the ever mounting political pressures) of using paper, cardboard, plastic, polystyrene, and metals for a variety of single-use, mainly disposable items such as containers, there has been an acute need (long since recognized by those skilled in the art) to find environmentally sound substitute materials, such as hydraulically settable materials, for these disposable items.
In spite of such pressures and long-felt need, the technology simply has not existed for the economic and feasible production of hydraulically settable materials which could be substituted for paper, cardboard, plastic, polystyrene, or metal sheets used to make a wide variety of disposable and nondisposable containers. However, because hydraulically settable materials essentially comprise such environmentally neutral components such as rock, sand, clay, and water, they would be ideally suited from an ecological standpoint to replace paper, cardboard, plastic, polystyrene, or metal materials as the material of choice for such applications.
Such materials are not only made from nondepletable components, they do not impact the environment nearly as much as do paper, cardboard, plastic, polystyrene, or metal. Another advantage of hydraulically settable and other inorganic materials is that they are far less expensive than paper, cardboard, plastic, polystyrene, or metals.
While paper, cardboard, plastic, polystyrene, and metal products might be comparably priced to each other, they are far more expensive than typical hydraulically settable materials. Because no rational business would ignore the economic benefit which would necessarily accrue from the substitution of significantly less expensive hydraulically settable materials for paper, cardboard, plastic, polystyrene, or metals, the failure to do so can only be explained by a marked absence of available technology to make such a substitution.
In light of the foregoing, what is needed are new materials other than paper, cardboard, plastic, polystyrene, or metal which can be used in the manufacture of containers used in storing, dispensing, and packaging liquids or solids. Such materials would represent a significant advancement in the art if they could be made without relying so heavily on the use of trees, petroleum, or other essentially nonrenewable or slowly renewing resources as the source of the primary starting material.
It would be a significant improvement in the art to provide compositions and methods which yielded hydraulically settable sheets and containers made therefrom which had properties similar to paper, cardboard, polystyrene, plastic, or metal. It would yet be a tremendous improvement in the art if such containers could be made using the same or similar manufacturing apparatus and techniques as those presently used to form containers from paper, cardboard polystyrene, plastic, or metal sheets.
It would yet be an important advancement in the art if such sheets and the containers made therefrom did not result in the generation of wastes involved in the manufacture of paper, cardboard, plastic polystyrene, or metals. In addition, it would be a significant improvement in the art if such sheets and the containers made therefrom were readily degradable into substances which are commonly found in the earth.
From a practical point of view it would be a significant improvement if such compositions and methods made possible the manufacture of containers at a cost comparable, or even superior to existing methods of manufacturing containers from existing materials. Specifically, it would be desirable to reduce the energy requirements and the initial capital investment costs for making products using existing materials.
From a manufacturing perspective, it would be a significant advancement in the art of cement making to provide cementitious mixtures and methods for mass producing cementitious sheets (and containers therefrom) which can rapidly be formed and substantially dried within a matter of minutes from the beginning of the manufacturing process.
Such materials used to manufacture food and beverage containers are disclosed and claimed herein.